The present invention is directed to a process for the production of calcium salts of hydantoic acids and specifically relates to the preparation of such acids from the corresponding hydantoin by treatment of the latter with a calcium base material.
D-p-hydroxyphenylglycine (DpHPG) is a key synthetic intermediate or building block for semi-synthetic penicillin and cephalosporins. There are various routes to prepare DpHPG and those include using hydantoins as an intermediate to the final DpHPG material. Such processes and other genetic processes for preparing glycines from hydantoins are generally disclosed in U.S. Pat. Nos. 5,147,664; 5,120,855; 4,960,932; 4,716,246; 4,621,153; 4,518,801; 4,436,910; 4,069,251; co-pending U.S. patent application Ser. No. 07/649,782 filed Jan. 31, 1991, entitled, "Precipitation-Induced Asymmetric Transformation of Chiral Alpha-Amino Acids and Salts Thereof", and which is assigned to the same Assignee as the present application; and Japanese patent application 55/104890 filed Aug. 11, 1980, and all of which are incorporated herein by reference in their entirety.
Some of the major problems with the processes disclosed in the prior art as exemplified by the above-identified patents and patent applications are the low yields of the desired end product and the formation of troublesome and unwanted by-products.
The disadvantages of the prior art are overcome by the present invention wherein there is provided a process for preparing hydantoic acids from their corresponding hydantoins by a very efficient and low cost method. The resultant hydantoic acids can then be subjected to a HNO.sub.2 -mediated decarbamoylation process followed by an optical resolution step to thus provide high yields of DpHPG.